Yeah,
There must have been a rash of Canon rear-element thieves many years ago.
If it stays cheap I might try, but it will end up a paperweight. If you ever run into a "shattered front-element" lens, it would be worth it. I paid $10 for a front element group (4 elements in a single module) for a Nikon 5cm F2. Once I find a lens with "heavy cleaning marks" for under $100, its mine.